const _lut: string[] = []
for (let i = 0; i < 256; i++) {
  _lut[i] = (i < 16 ? '0' : '') + i.toString(16)
}
export function uuid(): string {
  // http://stackoverflow.com/questions/105034/how-to-create-a-guid-uuid-in-javascript/21963136#21963136
  const d0 = Math.random() * 0xffffffff | 0
  const d1 = Math.random() * 0xffffffff | 0
  const d2 = Math.random() * 0xffffffff | 0
  const d3 = Math.random() * 0xffffffff | 0
  const uuid = _lut[d0 & 0xff] + _lut[d0 >> 8 & 0xff] + _lut[d0 >> 16 & 0xff] + _lut[d0 >> 24 & 0xff] + '-' + _lut[d1 & 0xff] + _lut[d1 >> 8 & 0xff] + '-' + _lut[d1 >> 16 & 0x0f | 0x40] + _lut[d1 >> 24 & 0xff] + '-' + _lut[d2 & 0x3f | 0x80] + _lut[d2 >> 8 & 0xff] + '-' + _lut[d2 >> 16 & 0xff] + _lut[d2 >> 24 & 0xff] + _lut[d3 & 0xff] + _lut[d3 >> 8 & 0xff] + _lut[d3 >> 16 & 0xff] + _lut[d3 >> 24 & 0xff] // .toUpperCase() here flattens concatenated strings to save heap memory space.

  return uuid.toUpperCase()
}
